The current technological trend of the lithium ion battery is to develop a high-capacity and high-power lithium ion battery, and therefore the performance and the safety thereof in a high temperature environment are key issues. The life of the lithium ion battery is significantly related to the stability of the materials of the anode and the cathode of the lithium ion battery. Inside the lithium ion battery, the electrolyte solution is in direct contact with the surface of the electrode material, and a chemical reaction occurs between the two during charge-discharge, producing byproducts and increasing impedance, and at the same time dissolving the metal and the oxygen ions of the electrode material. Therefore, the structure and the composition of the electrode material are changed. The phenomenon is particularly evident when using the battery at high temperature (above 45° C.) or because of heat runaway due to the battery generating electricity under high power. The battery performance declines rapidly from this phenomenon.
One known solution to above phenomenon is to coat a layer of high concentration metal ions on the surface of the active material of the electrode to reduce dissolution of the metal ions of the electrode material. Moreover, a protective layer is added to the surface of the active material of the electrode to improve the stability of the active material during charge-discharge at high temperature, whereby slowing the decline of the electrical properties of the battery. However, the protective layer may affect the ion transfer and the electron transfer between the active material of the electrode and the electrolyte solution, therefore decreasing the charge-discharge efficiency.